In related art, methods to measure sample temperature may be classified as a contact method, which typically employs a thermocouple or a resistance thermometer, or as a non-contact method, which typically employs an infrared radiation thermometer.
Since the contact method enables a configuration of an apparatus to be simple and inexpensive and a temperature of a sample to be directly measured, the contact method is widely used in various fields. However, the contact method is not an effective temperature measurement means with respect to a clean surface, a surface of a thin film in a thin film manufacturing process, or a sample of dimensions on the order of nanometers, since a sensor part of the thermocouple or the resistance thermometer is large and thermally contacts a measurement object.
In recent times, while local temperature measurement for Scanning Thermal Microscopy (SThM) has been attempted by installing a thermocouple or a resistance thermometer at an end of an Atomic Force Microscope (AFM) tip, definition of a measured physical value is unclear and simultaneous multi-functional measurement with another surface analysis measurement is impossible because of the required complexity of the measuring apparatus.
In addition, the infrared radiation thermometer, which is being widely distributed as a practical thermometer, measures thermal radiation from a surface of a material and determines the temperature of the material from a wavelength distribution or intensity of the thermal radiation. However, since an actual material is not an ideal blackbody radiation source, a thermal radiation amount from the surface of the material depends on thermo-optical properties (emissivity) of the surface. Accordingly, if there is no detailed information on the emissivity of the material, the surface temperature of the measurement object cannot be precisely measured.
As described above, due to the above-mentioned reasons, there is no practical temperature measuring means that can satisfy the following measurement needs in surface analysis or nano-scientific measurement fields: (a) locality (surface selectivity), (b) non-contact and (c) simultaneous multi-functional measurement.
Meanwhile, in the related art, it is well known that an energy distribution of electronic states of a material such as a metal is represented as a function of temperature by a Fermi distribution function, and such Fermi distribution is measured, so that the temperature of the material can be directly determined.
The Fermi distribution function is a probability distribution function of electrons depending on an absolute temperature T as represented by the following equation (1)
                              [                      Equation            ⁢                                                  ⁢            1                    ]                ⁢                                                                                                f          ⁡                      (                          E              ,              T                        )                          =                  1                                    exp              ⁡                              (                                                      E                    -                                          E                      F                                                                                                  k                      B                                        ⁢                    T                                                  )                                      +            1                                              (        1        )            
In the above equation (1), EF represents Fermi energy, kB represents the Boltzmann constant, and the function f(E,T) represents probability of electron occupancy in states at energy E.
Since the Fermi distribution function depends on only an absolute temperature T, when a Fermi distribution curve in a certain material can be obtained, the absolute temperature T of the material can be unambiguously determined from the Fermi distribution curve. When a technique of measuring a Fermi distribution of electrons with high resolution and determining a temperature of a material from the Fermi distribution function is developed, temperature measurement that satisfies the above conditions (a) to (c) becomes possible.
In the related art, measurement of electron energy states of a material may contains include such methods as scanning tunneling microscopy (STM), ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), or Auger electron spectroscopy (AES).
While STM is appropriate for measuring local density of states, intensity of tunnel current that can be obtained through the measurement is overlap integral between electronic states of a sample and a metal tip, and Fermi distribution of electrons in the sample cannot be directly measured.
Meanwhile, UPS or XPS uses an apparatus for applying irradiating light in an ultraviolet or x-ray region to a sample and measuring the kinetic energy of excited electrons emitted from the sample. A high energy edge of such an electron spectrum is due to photoelectron emission from a state at Fermi energy (EF) of the sample, and the shape of the high energy edge of the photoelectron spectrum reflects the Fermi distribution of the sample.
In addition, XPS or AES employs an excitation source of several keV, which is appropriate to chemical analysis measuring an inner shell electron. Further, in order to measure electronic states of a valence band around the Fermi energy with high energy resolution, UPS is optimal. Further, in UPS, since an escape depth of the electrons excited by light in an ultraviolet region or a vacuum ultraviolet region is several angstroms, information on the electronic states in several atomic layers on the surface can be obtained.
Conventional electron energy analyzers used in electron spectroscopy (UPS, XPS, or AES) may be categorized as a retarding electric field type or as an electrostatic deflection type. The retarding electric field type uses a method of analyzing electron energy by passing only electrons with kinetic energy higher than potential of the retarding electrodes (barrier potential) and preventing electrons with lower energy from passing, which is conventionally used to measure electrons with relatively high energy of several keV with no necessity for high energy resolution. The electrostatic deflection type is used to measure the energy of electrons smaller than several keV with high energy resolution.
In particular, in measurement by UPS for material investigations, angle-resolved measurement of electrons emitted from a sample is important, and mainly a concentric electrostatic hemispherical analyzer with an angular resolution is used, Chemical Society of Japan, Chemical Reviews, No. 16, Electron Spectroscopy, Academic Press Center, Published on Jul. 10, 1977, pages 20 to 25.
Meanwhile, in AES, a hemispherical retarding type analyzer is often used. Since the hemispherical retarding type analyzer detects electrons in a wide detection angle (a solid angle), in comparison with a concentric electrostatic hemispherical analyzer, in general, measurement with high sensitivity is possible with a hemispherical retarding type analyzer.